Preservative System

ABSTRACT

Provided herein is a cost-effective and potent preservative system for a composition comprising a salicylate salt and a benzoate salt in an amount of from 0.2 weight % to 0.5 weight % by total weight of the composition and in a molar ratio of salicylate to benzoate of 1:6 to 1:1.2, wherein the composition has a pH of 5 or less. Further provided herein is a method of using a combination of a salicylate salt and a benzoate salt in a preservative system in a composition, and a method of preserving a composition.

BACKGROUND

Preservative agents are incorporated into personal care compositionssuch as body lotions, ointments, creams and salves, to inhibit microbialgrowth that may, for example, arise from contamination by the consumerwhen in use.

Salicylate salts are effective preservative agents. However, salicylatesalts are relatively expensive to use.

Therefore, it would be desirable to provide alternative preservativesthat are cost-effective and effective in inhibiting microbial growth.

BRIEF SUMMARY

A composition comprising a preservative system, wherein the preservativesystem comprises a salicylate salt and a benzoate salt, wherein a totalamount of the salicylate salt and the benzoate salt is from 0.2 to 0.5weight % by total weight of the composition, wherein a molar ratio ofthe salicylate to the benzoate is 1:5.55 to 1:1.11, and wherein the pHof the composition is 5 or less.

Optionally, the preservative system consists of the salicylate salt andthe benzoate salt. Further optionally, the composition is free ofpreservatives other than those of the preservative system.

Typically, the salicylate salt comprises sodium salicylate, and/or thebenzoate salt comprises sodium benzoate.

In another aspect, provided is the use of a combination of a salicylatesalt and a benzoate salt of any of the compositions defined herein as apreservative system in the composition.

In another aspect, provided is a method of preserving a compositioncomprising adding the preservative system defined herein to thecomposition.

Further areas of applicability of the present invention will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred embodiment of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

DETAILED DESCRIPTION

The following description of the preferred embodiment(s) is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses.

As used throughout, ranges are used as shorthand for describing each andevery value that is within the range. Any value within the range can beselected as the terminus of the range. In addition, all references citedherein are hereby incorporated by referenced in their entireties. In theevent of a conflict in a definition in the present disclosure and thatof a cited reference, the present disclosure controls.

The term “preservation” in the context of the present invention refersto the prevention or retardation of product deterioration due tomicroorganisms present in the product. A “preservative agent” or“preservative” in the context of the present invention is a substancethat prevents or retards the growth of microorganisms in a product.

Unless otherwise specified, all percentages and amounts expressed hereinand elsewhere in the specification should be understood to refer topercentages by weight. The amounts given are based on the active weightof the material, as present in the mentioned compositions.

In one arrangement, the present invention provides a compositioncomprising a preservative system, wherein the preservative systemcomprises a salicylate salt and a benzoate salt, wherein the totalamount of the salicylate salt and the benzoate salt is 0.2 weight % toabout 0.5 weight % by total weight of the composition. In anotherarrangement, the total amount of the salicylate salt and the benzoatesalt is 0.2 weight % to about 0.6 weight % by total weight of thecomposition.

Salicylate and Benzoate Salt

In some embodiments, the total amount of the salicylate salt and thebenzoate salt is 0.25, 0.3, or 0.4 weight %, to 0.5 or 0.6 weight % bytotal weight of the composition. In a preferred embodiment, the totalamount of the salicylate salt and the benzoate salt is 0.25 to 0.5weight %, or 0.3 to 0.5 weight %, or 0.35 to 0.5 weight %, or 0.4 to 0.5weight % by total weight of the composition. Optionally, the totalamount of the salicylate salt and the benzoate salt is from 0.2 weight %or 0.25 weight % to 0.4 weight % by total weight of the composition.Further optionally, the total amount of the salicylate salt and thebenzoate salt is 0.2 weight %, 0.25 weight %, 0.3 weight %, 0.35 weight%, 0.4 weight %, 0.45 weight %, or 0.5 weight % by total weight of thecomposition. Preferably, the total amount of the salicylate salt and thebenzoate salt is 0.4 weight % of the total weight of the composition. Itis understood that any of the mentioned concentrations may be used incombination with any of the weight ratios of salicylate salt to thebenzoate salt as defined below.

In some embodiments, the molar ratio of the salicylate to the benzoateis 1:6 to 1:1.2, 1:5 to 1:1.2, 1:4.5 to 1:1.2, 1:4 to 1:1.2, 1:3.5 to1:1.2, or 1:3 to 1:1.2, 1:2.5 to 1:1.2, 1:2 to 1:1.2, 1:5.55 to 1:1.11,1:4.995 to 1:1.11, 1:4.44 to 1:1.11, 1:3.885 to 1:1.11, 1:3.33 to1:1.11, 1:2.775 to 1:1.11, 1:2.22 to 1:1.11, or 1:1.665 to 1:1.11. Inone embodiment, the molar ratio of the salicylate salt to the benzoatesalt is 1:5.55 to 1:4.44, 1:5.55 to 1:3.33, 1:5.55 to 1:2.22, or 1:5.55to 1:1.11. In other embodiments, the molar ratio of the salicylate saltto the benzoate salt is 1:5.217 to 1:3.33, 1:5.217 to 1:2.22, or 1:5.217to 1:1.11. In yet other embodiments, the molar ratio of the salicylateto the benzoate may be 1:4.44 to 1:3.33, 1:4.44 to 1:2.22, or 1:3.33 to1:2.22. The molar ratio of the salicylate to the benzoate may be 1:5.55,1:5.217, 1:4.995, 1:4.44, 1:3.33, 1:3.885, 1:2.775, 1:2.22, 1:1.665, or1:1.11. Reducing the proportion of salicylate is advantageous assalicylate is an expensive preservative agent. Increasing the proportionof salicylate beyond a salicylate:benzoate molar ratio of 1:1.11 is notdesirable due to increased manufacturing costs.

Typically at these molar ratios, the pH of the composition is between 4and 4.5, and preferably between 4 and 4.25. Most preferably, at thesemolar ratios, the pH of the composition is around 4. Typically at thesemolar ratios, the total concentration of the salicylate salt and thebenzoate salt is greater than 0.25 or 0.3 weight % by total weight ofthe composition. Preferably at these molar ratios, the totalconcentration of the salicylate salt and the benzoate salt is 0.3 weight% to 0.4 weight % or 0.5 weight % or 0.6 weight % by total weight of thecomposition.

Typically, the salicylate salt is sodium salicylate and/or the benzoatesalt is sodium salicylate. However, other salicylate and/or benzoatesalts may be used in the preservative system. These include potassiumsalicylate and potassium benzoate.

In some embodiments for sodium salicylate and sodium benzoate, theweight ratio of the sodium salicylate to the sodium benzoate is 1:5 to1:1, 1:4.5 to 1:1, 1:4 to 1:1, 1:3.5 to 1:1, 1:3 to 1:1, 1:2.5 to 1:1,1:2 to 1:1 or 1:1.5 to 1:1. In one embodiment, the weight ratio of thesodium salicylate to the sodium benzoate is 1:5 to 1:4, or 1:5 to 1:3 or1:5 to 1:2 or 1:5 to 1:1. In other embodiments, the weight ratio of thesodium salicylate to sodium benzoate is 1:4.7 to 1:3 or 1:4.7 to 1:2 or1:4.7 to 1:1. In yet other embodiments, the weight ratio of the sodiumsalicylate to the sodium benzoate may be 1:4 to 1:3, 1:4 to 1:2, or 1:3to 1:2. The weight ratio of the sodium salicylate to the sodium benzoatemay be 1:5, 1:4.7, 1:4.5, 1:4, 1:3, 1:3.5, 1:2.5, 1:2, 1:1.5, or 1:1.Reducing the proportion of salicylate is advantageous as salicylate isan expensive preservative agent. Increasing the proportion of salicylatebeyond a sodium salicylate:sodium benzoate weight ratio of 1:1 is notdesirable due to increased manufacturing costs.

Typically at these weight ratios, the pH of the composition is between 4and 4.5, and preferably between 4 and 4.25. Most preferably, the atthese weight ratios, the pH of the composition is around 4. Typically atthese weight ratios, the total concentration of the sodium salicylateand the sodium benzoate salt is greater than 0.25 or 0.3 weight % bytotal weight of the composition. Preferably at these weight ratios, thetotal concentration of the sodium salicylate and the sodium benzoate is0.3 weight % to 0.4 weight % or 0.5 weight % or 0.6 weight % by totalweight of the composition.

Preservative System

The preservative system of the present invention provides a highlyeffective preservative function, thereby obviating the need for anyother preservative agents. In particular, salicylate and benzoate saltsact in combination, in a low total concentration, to provide a highlyeffective system, obviating the need for further preservative agents.This enables the compositions to have reduced manufacturing costs andreduced toxicity effects that may arise from other preservative agents.

Therefore, in one embodiment, the preservative system consists of thesalicylate salt and the benzoate salt. Preferably, the composition isfree of preservatives other than those of the preservative system.

pH

Typically, the pH of the compositions of the present invention is 5 orless, and optionally, from 4 to 5. The inventors have found that whenthe pH is increased beyond 5, the preservative function of salicylateand benzoate is diminished. The pH of the compositions may be 4 to 4.5,4.5 to 5 or 4.25 to 4.75. In some embodiments, the pH is 4, about 4.25,4.5, 4.75 or 5. As the pH is decreased from 5, the preservative functionof salicylate and benzoate is increased.

Form of Composition

Typically, the compositions of the present invention are aqueous. Thecarrier of the compositions may comprise demineralized water and/orsoftened water. Water is typically present in the compositions in anamount that is sufficient to form a liquid composition. In certainembodiments, the amount of water is at least 50 weight %, or 50 weight %to 90 weight % by total weight of the composition. In other embodiments,the amount of water is from 55 weight % to 70 weight % by total weightof the composition.

Typically, the compositions of the present invention are liquidcompositions, and preferably, liquid cleansing compositions, and maytake the form of a liquid, gel, lotion or foam. The compositionsaccording to the present invention are preferably suitable for topicalapplication to the skin and/or nails. The compositions may be applied tothe skin and/or nails for therapeutic, prophylactic or cosmetic benefit.The compositions according to the present invention may for example beused for enhancing the appearance, cleansing, controlling or improvingodor, and improving the feel of skin and/or nails.

The composition of the present invention may be provided, withoutlimitation, in the form of a body wash, shower gel or a liquid soap.

In some embodiments, the compositions may further comprisepharmaceutically or cosmetically active agents which provide a cosmetic,therapeutic or prophylactic benefit to the skin. For example, thecompositions may comprise at least one cosmetically acceptable carrierselected from surfactants, humectants, emollients, thickeners,fragrances, stabilizers, colorants, antioxidants, dyes and skin careagents. Such agents and the amounts in which they may be incorporatedwould be known to those of ordinary skill in the art. Non-limitingexamples of some such agents are provided below.

In other embodiments, the compositions of the present invention may beoral care compositions, such as dentifrice or mouthrinse compositions.In yet further embodiments, the compositions of the present inventionmay be antiperspirant or deodorant compositions.

Surfactants

The compositions according to the present invention may include one ormore anionic surfactants, amphoteric surfactants, nonionic surfactants,cationic surfactants, and combinations thereof. Surfactants can beincluded in any desired amount. In one embodiment, surfactants arepresent in the composition in an amount of 0 to about 40% by weight. Inone embodiment, the surfactants are present in an amount of about 1 toabout 40% by weight. In one embodiment, surfactants are present in thecomposition in an amount of about 5 to about 40% by weight. In oneembodiment, the surfactants are present in an amount of about 1 to about10% by weight.

Anionic surfactants include, for example, long chain (C₆-C₂₂) alkylmaterials such as long chain alkyl sulfates, long chain alkylsulfonates, long chain alkyl phosphates, long chain alkyl ethersulfates, long chain alkyl alpha olefin sulfonates, long chain alkyltaurates, long chain alkyl isethionates (SCI) long chain alkyl glycerylether sulfonates (AGES), sulfosuccinates and the like. Other anionicsurfactants include sodium laureth sulfate, sodium pareth sulfate, andcombinations thereof.

Amphoteric surfactants include, but are not limited to, derivatives ofsecondary and tertiary aliphatic amines in which the aliphatic radicalis straight chain or branched and wherein one of the aliphaticsubstituents comprises about 8 to about 18 carbon atoms and one containsan anionic water solubilizing group, e.g., carboxy, sulfonate, sulfate,phosphate, or phosphonate. Examples of such compounds include sodium3-dodecyaminopropionate, sodium 3-dodecylaminopropane sulfonate, N-alkyltaurines and N-higher alkyl aspartic acids. Other equivalent amphotericsurfactants may also be used. These include high alkyl betaines such ascoco dimethyl carboxymethyl betaine, lauryl dimethyl carboxy-methylbetaine, lauryl dimethyl alpha-carboxyethyl betaine, cetyl dimethylcarboxymethyl betaine, lauryl bis-(2-hydroxyethyl)carboxy methylbetaine, stearyl bis-(2-hydroxypropyl)carboxymethyl betaine, oleyldimethyl gamma-carboxypropyl betaine, and laurylbis-(2-hydroxypropyl)alpha-carboxyethyl betaine, sulfobetaines such ascoco dimethyl sulfopropyl betaine, stearyl dimethyl sulfopropyl betaine,amido betaines, amidosulfobetaines and the like.

Examples of nonionic surfactants include, but are not limited to,polysorbate 20, long chain alkyl glucosides having C₈-C₂₂ alkyl groups,coconut fatty acid monoethanolamides such as cocamide MEA, coconut fattyacid diethanolamides, fatty alcohol ethoxylates (alkylpolyethyleneglycols), alkylphenol polyethylene glycols, alkyl mercaptan polyethyleneglycols; fatty amine ethoxylates (alkylaminopolyethylene glycols), fattyacid ethoxylates (acylpolyethylene glycols), polypropylene glycolethoxylates (for example the PLURONIC™ block copolymers commerciallyavailable from BASF), fatty acid alkylolamides, (fatty acid amidepolyethylene glycols), N-alkyl-, N-alkoxypolyhydroxy fatty acid amides,sucrose esters, sorbitol esters, polyglycol ethers, and combinationsthereof.

Examples of cationic surfactants include, but are not limited to, anyquaternium or polyquaternium compound.

In another arrangement, the present invention provides a method of usinga combination of a salicylate salt and a benzoate salt in a preservativesystem in a composition, wherein the total amount of the salicylate saltand the benzoate salt in the composition is from 0.2 to 0.5 weight % bytotal weight of the composition. The composition may be as definedherein.

In yet another arrangement, the present invention provides a use of acombination of a salicylate salt and a benzoate salt as a preservativesystem in a composition, wherein the total amount of the salicylate saltand the benzoate salt in the composition is from 0.2 to 0.5 weight % bytotal weight of the composition.

In a further arrangement, the present invention provides a method ofpreserving a composition comprising incorporating into the composition apreservative system, wherein the preservative system comprises asalicylate salt and a benzoate salt, wherein the total amount of thesalicylate salt and the benzoate salt in the composition from 0.2 to 0.5weight % by total weight of the composition. The composition may be asdefined herein.

EXAMPLES Example 1—Minimum Inhibitory Concentration Test

A minimum inhibitory concentration (MIC) test was carried out todetermine the effect of the weight ratio of salicylate:benzoate and pHon the growth inhibition of B. cepecia, P. aeruginosa, E. coli, Saureus, C. albicans and A. niger.

In order to determine the minimum inhibitory concentration for each testratio/pH, a culture of the relevant microorganism was grown, serialdilutions of the test salicylate/benzoate composition were prepared, anda standard volume of each dilution was incubated with a standard volumeof the culture. Growth of the microorganism was assessed by measuringthe turbidity of the sample.

A preservative is deemed effective when growth of the microorganism isobserved only when the dilution til growth (DTG) number is 6 or more. Ahigher DTG number indicates enhanced mirorobustness. It was observedthat for the microorganisms tested, an adequate inhibition of growth wasobserved when the pH was less than 5. B. cepecia was the most resistantto the test salicylate/benzoate compositions, and therefore used as themodel organism in subsequent microrobustness tests (see below). The pHeffect is very strong with higher DTG at a pH of 4.5. As the pHincreased, DTG decreased.

Example 2—Screening

Sodium salicylate and sodium benzoate were incorporated into a baseformula typically used as a cleansing composition, in varying weightratios, to find an effective preservative system. The base formula isillustrated in Table 1.

TABLE 1 Base formula used to screen sodium salicylate and sodiumbenzoate combinations % weight in Ingredients Formula DemineralizedWater Q.S. Softened Water 20-22 Alkyl Ether Sulfate (Steol OS-270) 10-13Polyquatemium-7 1-3 CAP Betaine  8-11 Decyl Glucoside 1-3 TetrasodiumEDTA - 39% Soln. 0.1-0.3 Citric Acid - 50% Solution - Food 0.1-1   Grade

Samples of the base formula comprising sodium salicylate and sodiumbenzoate in different weight ratios, and in a total amount of 0.6 weight%, were subjected to a Micro Robustness Test (MRT) to assess theantimicrobial efficacy of the preservatives against Burkholderiacepacia. Samples of the base formula were challenged with an inoculum ofbacteria. After 2, 6 and 24 hours, aliquots were tested to measure thelog reduction of bacteria. Using these data, the area under the growthreduction curve (AUC) was calculated and normalized (NAUC). The AUCvalues represent both the rate of growth inhibition and total amount ofgrowth inhibition. An AUC value of greater than 75 indicates acceptablepreservative function.

The results are presented in Table 2.

TABLE 2 MRT test results (1) Log Reduction Summary Sample Description 26 24 # (weight %) Hour Hour hour AUC NAUC 1 Base with 0% Sodium 5.725.26 6.72 135.00 135.68 Benzoate/100% Sodium Salicylate, pH = 4.5 2 Basewith 25% Sodium 5.46 5.24 6.72 134.50 135.18 Benzoate/75% SodiumSalicylate, pH = 4.5 3 Base with 50% Sodium 4.42 5.10 6.72 129.84 130.49Benzoate/50% Sodium Salicylate, pH = 4.5 4 Base with 75% Sodium 2.785.13 6.72 125.78 126.41 Benzoate/25% Sodium Salicylate, pH = 4.5 5 Basewith 100% Sodium 1.02 1.13 3.72 48.97 49.22 Benzoate/0% SodiumSalicylate, pH = 4.5 6 Base with 0% Sodium 0.52 0.44 0.87 14.23 14.30Benzoate/0% Sodium Salicylate, pH = 4.5 7 Base with 0% Sodium 4.08 5.276.72 130.69 131.35 Benzoate/100% Sodium Salicylate, pH = 5.0 8 Base with25% Sodium 2.93 5.14 6.72 125.81 126.44 Benzoate/75% Sodium Salicylate,pH = 5.0 9 Base with 50% Sodium 2.15 4.06 6.72 111.59 112.15Benzoate/50% Sodium Salicylate, pH = 5.0 10 Base with 75% Sodium 1.881.49 6.72 82.50 82.91 Benzoate/25% Sodium Salicylate, pH = 5.0 11 Basewith 100% Sodium 0.95 0.92 4.00 48.97 49.22 Benzoate/0% SodiumSalicylate, pH = 5.0 12 Base with 0% Sodium 0.44 0.46 0.52 11.06 11.12Benzoate/0% Sodium Salicylate, pH = 5.0

It can be seen from Table 2 that when the weight ratio of salicylate tosodium benzoate is as low as 1:3 (i.e. 25 weight % salicylate, and 75weight % benzoate), adequate microrobustness is achieved. However, whensalicylate is absent (see Formula 11), adequate microrobustness is notachieved.

Example 2

The preservative action of sodium salicylate and sodium benzoate invarying weight ratios and in varying total amounts was determined in amicrorobustness test as described above. The results are illustrated inTable 3.

TABLE 3 MRT test results (2) Retest Results Sample Sample Description 26 24 # (weight %) Hour Hour Hour AUC NAUC 1 Base w/50% Sodium 2.42 5.485.90 120.64 137.08 Benzoate/50% Sodium Salicylate pH 4.5 conc. 0.4% 2Base w/50% Sodium 3.08 5.01 6.68 124.47 141.43 Benzoate/50% SodiumSalicylate pH 4.5 conc. 0.6% 3 Base w/75% Sodium 1.68 3.53 2.68 67.9977.25 Benzoate/25% Sodium Salicylate pH 4.5 conc. 0.5% 4 Base w/100%Sodium 0.48 0.53 2.32 28.15 31.99 Benzoate/0% Sodium Salicylate pH 4.5conc. 0.4% 5 Base w/100% Sodium 0.68 1.42 5.03 62.93 71.50 Benzoate/0%Sodium Salicylate pH 4.5 conc. 0.6% 6 Base w/50% Sodium 2.28 5.16 6.68123.72 140.57 Benzoate/50% Sodium Salicylate pH 4.75 conc. 0.5% 7 Basew/75% Sodium 0.80 1.87 5.64 73.73 83.77 Benzoate/25% Sodium SalicylatepH 4.75 conc. 0.4% 8 Base w/75% Sodium 1.10 2.57 5.28 79.09 89.86Benzoate/25% Sodium Salicylate pH 4.75 conc. 0.5% 9 Base w/75% Sodium1.05 2.53 6.68 91.10 103.51 Benzoate/25% Sodium Salicylate pH 4.75 conc.0.5% 10 Base w/75% Sodium 1.28 3.12 6.68 98.28 111.67 Benzoate/25%Sodium Salicylate pH 4.75 conc. 0.6% 11 Base w/100% Sodium 0.30 0.573.88 42.09 47.82 Benzoate/0% Sodium Salicylate pH 4.75 conc. 0.5% 12Base w/50% Sodium 0.86 2.08 6.20 81.26 92.33 Benzoate/50% SodiumSalicylate pH 5.0 conc. 0.4% 13 Base w/50% Sodium 1.45 3.57 2.68 67.7476.97 Benzoate/50% Sodium Salicylate pH 5.0 conc. 0.6% 14 Base w/75%Sodium 1.06 1.89 6.68 84.09 95.55 Benzoate/25% Sodium Salicylate pH 5.0conc. 0.5% 15 Base w/100% Sodium 0.42 0.28 0.60 9.74 11.07 Benzoate/0%Sodium Salicylate pH 5.0 conc. 0.4% 16 Base w/100% Sodium 0.79 0.57 0.9417.10 19.43 Benzoate/0% Sodium Salicylate pH 5.0 conc. 0.6%

It can be seen from Table 3 that when the salicylate:benzoate weightratio is as low as 1:3 (i.e. 25 weight % salicylate, and 75 weight %benzoate), and the total concentration of salicylate and benzoate is aslow as 0.4 weight %, adequate microrobustness is achieved. However, inthe absence of salicylate (see Formulae 15 and 16), adequatemicrorobustness is not achieved.

Example 3—pH Testing

The preservative action of sodium salicylate and sodium benzoate invarying weight ratios of up to 1:3 (i.e. 25 weight % salicylate, and 75weight % benzoate), under varying pH conditions ranging from 4 to 4.5,and in varying total amounts, was determined in a microrobustness testas described above. The results are illustrated in Table 4. It can beseen from Table 4 that when the salicylate:benzoate weight ratio is aslow as 1:5 (i.e. 17.5 weight % salicylate, and 82.5 weight % benzoate),adequate microrobustness is achieved at pH values of 4 to 4.5. However,when the weight ratio of salicylate:benzoate is reduced further (e.g.10% salicylate:90% benzoate), adequate microrobustness is not achieved.

TABLE 4 Preservative function with varying pH, varyingsalicylate:benzoate ratios, and varying total concentration ofsalicylate and benzoate. Preserv % salic by # pH level weight AUC 2 H 6H 24 H 1 4.5 0.2 25 69.65 1.07 1.27 5.83 2 4.5 0.25 17.5 71.09 1.23 1.755.35 3 4.25 0.25 10 68.84 1.60 1.51 5.27 4 4 0.2 25 60.4 1.05 1.22 4.875 4.5 0.3 10 66.56 1.27 1.63 4.98 6 4.5 0.3 25 87.12 1.51 1.92 6.83 74.25 0.25 17.5 84.14 1.37 2.08 6.35 8 4.25 0.3 17.5 80.41 1.65 2.09 5.839 4 0.25 17.5 100.31 2.02 2.98 6.83 10 4.5 0.2 10 49.61 0.79 1.12 3.8811 4.25 0.25 25 86.34 1.51 2.34 6.23 12 4 0.2 10 74.81 1.47 1.63 5.83 134.25 0.2 17.5 73.39 1.53 1.55 5.75 14 4.25 0.25 17.5 81.77 1.60 1.906.23 15 4 0.3 25 126.28 3.05 5.06 6.83 16 4 0.3 10 81.79 1.68 1.88 6.23

Example 4—pH Testing (2)

The preservative action of sodium salicylate and sodium benzoate invarying weight ratios of up to 1:1, under varying pH conditions rangingfrom 4 to 5, and in varying total amounts, was determined in amicrorobustness test as described above. It was observed that when thesalicylate:benzoate weight ratio is as low as 1:5 (i.e. about 17 weight% salicylate, and about 83 weight % benzoate) and up to 1:1 (i.e. 50weight % salicylate, and 50 weight % benzoate), adequate microrobustnessis achieved at pH values of 4 to 5 and at a total salicylate andbenzoate concentration of 0.2 to 0.6 weight %. However, when theproportion of salicylate is reduced further, the microrobustness of thepreservative system decreases. It may also be seen that growthinhibition using a salicylate:benzoate ratio of from 1.5 to 1:1 is moreeffective when the pH is from 4 to 4.5 than when the pH is from 4.5 to5.

We claim:
 1. A composition comprising a preservative system, wherein thepreservative system comprises a salicylate salt and a benzoate salt,wherein a total amount of the salicylate salt and the benzoate salt isfrom 0.2 to 0.5 weight % by total weight of the composition, wherein amolar ratio of the salicylate to the benzoate is 1:6 to 1:1.2, andwherein the pH of the composition is 5 or less.
 2. The composition ofclaim 1, wherein the molar ratio of the salicylate salt to the benzoatesalt is 1:4.5 to 1:1.2.
 3. The composition of claim 1, wherein the molarratio of the salicylate salt to the benzoate salt is 1:3.4 to 1:1.2. 4.The composition of claim 1, wherein the molar ratio of the salicylatesalt to the benzoate salt is 1:6 to 1:2.3 or 1:6 to 1:3.4.
 5. Thecomposition of claim 1, wherein the molar ratio of the salicylate saltto the benzoate salt is 1:3.33.
 6. The composition of claim 1, whereinthe salicylate salt comprises sodium salicylate.
 7. The composition ofclaim 1, wherein the benzoate salt comprises sodium benzoate.
 8. Thecomposition of claim 1, wherein the preservative system consists of thesalicylate salt and the benzoate salt.
 9. The composition of claim 1,wherein the composition is free of preservatives other than those of thepreservative system.
 10. The composition of claim 1, wherein the totalamount of the salicylate salt and the benzoate salt is 0.3 to 0.5 weight%, by total weight of the composition.
 11. The composition of claim 1,wherein the total amount of the salicylate salt and the benzoate salt is0.4 to 0.5 weight %, by total weight of the composition.
 12. Thecomposition of claim 1, wherein the total amount of the salicylate saltand the benzoate salt is 0.4 weight % by total weight of thecomposition.
 13. The composition of claim 1, wherein the pH of thecomposition is 4 to
 5. 14. The composition of claim 1, wherein the pH ofthe composition is 4 to 4.5.
 15. The composition of claim 1, wherein thesalicylate salt is sodium salicylate and the benzoate salt is sodiumbenzoate, and a weight ratio of sodium salicylate to sodium benzoate is1:5 to 1:1.
 16. The composition of claim 15, wherein the weight ratio ofsodium salicylate to sodium benzoate is 1:4.7 to 1:3.
 17. Thecomposition of claim 15, wherein the weight ratio of sodium salicylateto sodium benzoate is one of 1:5, 1:4.7, 1:4.5, 1:4, 1:3, 1:3.5, 1:2.5,1:2, or 1:1.5.
 18. The composition of claim 1, wherein the compositionis a liquid cleaning composition.
 19. A method of preserving acomposition comprising adding the preservative system of claim 1 to thecomposition.
 20. (canceled)